Which of the following is not a ground of divorce under section 2 of the Dissolution of Muslim Marriage…

Under Section 2 of the Dissolution of Muslim Marriages Act, 1939 the ground is that the husband's whereabouts have not been known for four years, so "Whereabouts of the husband have not been known for a period of 3 years." is not a ground, while imprisonment for seven years, failure to maintain for two years and failure to perform marital obligations for three years are grounds.